* Fix plugin API in globally installed Prettier and introduce optional --plugin-search-dir
* Use find-parent-dir instead of find-up and test autoloading (with mocked fn)
* Add two test cases where --plugin-search-dir is not .
* Do not mutate pluginSearchDirs argument in load-plugins.js
* Do not test automatic plugin resolution as mocking of "find-parent-dir" does not work due to rollup
* Document --plugin-search-dir / pluginSearchDirs and improve spacing
* Address @ikatyang's review comments
* Fix require path for third-party
* Undo alphabetic sorting of third-party scripts